Interesting Case

[sphelps]

I met another reefer the other night and I was taking a look at his tank and talking about some of the routine maintenance he performs and I was blown away to discover he has to clean his return pump and skimmer pump every 2 weeks or they will physically stop working due to lime build up. It’s become such a routine that he has two spare pumps which he switches out every two weeks. The pumps are MAG 1800, his tank volume is about 160 gallons and it’s moderately stocked with about a dozen smaller SPS colonies, 3 clams at 4” and maybe half a dozen larger LPS corals. I wouldn’t consider it a high demand tank but he claims he needs to dose 400mL/day of Calcium and 800mL/day of Alk supplement just to keep his calcium at about 420 and Alk at about 8.2. He’s using Randy’s recipe #1 and he also doses Kalk through his top off.

It seems obvious he’s overdosing a ton but his PH sits at 8.2 and he claims he’s verified his test readings multiple times with different tests kits including Salifert, Seachem and Hanna. The recommended dosage for his tank should be in the range of 80mL/day but he’s dosing 5 to 10 times that plus the Kalk.

I thought it was a bit of an interesting case so I’m opening it up for discussion. All his corals look fairly healthy, SPS are a little washed out but he’s using a lot of carbon and GFO. He also skims very wet and consistently changes water weekly at a rate of about 5%, uses H2Ocean salt and RO/DI.

[mark]

Been using a reactor for my needs but go years between cleaning on my pumps and even then it's more just a thin slime coat.

Every 2 weeks, is he dosing directly in front of the pump's intakes?

[sphelps]

Originally Posted by mark

Been using a reactor for my needs but go years between cleaning on my pumps and even then it's more just a thin slime coat.

Every 2 weeks, is he dosing directly in front of the pump's intakes?

Not really, he doses directly into sump after skimmer and a couple chambers back from return.

[phi delt reefer]

maybe a second set of eyes should check his testing. those tests all use a color scale and he could be interpreting them wrong or looking at them in the wrong light, etc.

Sphelps - maybe he can bring you a water sample and you could test it and report back?

[cathyg_99]

maybe his RO unit isnt filtering enough out of the water? thats why hes getting a build up... as for the dosing that seems really high, id have someone else do my testing for me

[Aquaria]

It's got nothing to do with the rodi I know people who use tap water and if that's the case should they not have the same problems?

[Delphinus]

My guess is low magnesium. Before I would track magnesium, I noticed calcium buildup on many of my pump's magnets and shafts. Powerheads .. skimmer pumps .. etc. Calcium precipitates easily when Mg is low. This effect has been profoundly reduced since keepng Mg where it should be. Now I still notice some buildup on the Tunze magnets but nothing that needs to be removed more than say once every 6 months or so.

[Lance]

Does the sump chamber where he doses have fairly low flow, or is he dosing the calcium and alk too soon to each other? I had the same problem for awhile in the 90g, (though not as extreme). I use the same recipe, and found if I dose the calcium and the alk into the same chamber I have to make sure there is at least 6 hours between the dosing times or I get calcification. In fact the water in that chamber was even a little milky from the two reacting together. I eventually moved the calcium dosing line to a different part of the sump that has more flow and that helped a lot. Within days after doing this the volume of calcium and alk I needed to dose to keep parameters in line dropped considerably.

[asylumdown]

This sounds exactly like what was happening to me when my water chemistry went weird.

a) what alk supplement is he using? is it baking soda from a grocery store, or something prepared specially for reef tanks? I know they're supposed to be essentially the same, but when I used baking soda, my water chemistry went haywire, and the ratios of solution made no sense. I also ended up with pumps failing weekly due to precipitation.

b) is he adding carbonate or bicarbonate as his alk source (carbonate would be if he's 'cooking' his bicarbonate)? With pH levels and dosing volumes both being that high, I suspect he's adding something with a lot of carbonate, which is considerably less soluble and more likely to precipitate out than bicarbonate.

c) It sounds like he's adding so much carbonate/bicarbonate that his levels are never balanced. Is he using an auto-doser? If he's pushing one past the 'limit', addition of the other will instantly react and precipitate out. I think you can get in to a vicious cycle. I bet at one point in the past he overdosed on one additive (likely alk), which caused a precipitation reaction that depressed his levels of calcium. On a test kit, it would have looked like he had low calcium and normal alkalinity. If he's using a doser, he would have then upped the amount of calcium he was adding every day. However, there would still be excess carbonate being added, so the precipitation would continue, and appear to depress his alk levels. So then he upped the amount he dosed alk, which would depress the calcium levels again... so on and so forth, always upping one, seeing a drop in the other, upping it, then seeing a drop on the other side. The end result would still look like he has 'normal' levels in his water, but that's because massive amounts are instantly precipitating out on pumps, etc. If this is the case, he needs to start dialing back on the amounts he's adding in the same way he upped his dosing volumes.

In either case, there's no other answer, he's adding too much. That's the only explanation for the precipitation. The 'normal' levels he's seeing aren't 'normal' at all, they're what's left over after the precipitation of the excess he's added to the system.

[asylumdown]

To add:

If you're finding that you're adding twice as much alk as calcium and you keep upping the amounts of each, I think you should first try dialing way back on the rate you dose alk. It seems counter intuitive, but if you're precipitating out large amounts of additive due to an imbalance, you're not likely going to see normal levels in one, and way high levels in the other, it will look like 'normal' levels of the one you're over-dosing, and low levels of the other.